Method and apparatus for the continuous withdrawal of samples from industrial process baths or the like for analysis

ABSTRACT

A method and apparatus is disclosed for drawing a filtered sample from a solution or bath, especially an industrial process bath, for continuous or continual analysis. This invention involves periodically blowing a suitable pressurized fluid medium compatible with the bath, that is one which does not affect the sampling process, typically air, although other media can be employed, into the sampling bath on the downstream side of a filter. Backwash of the filter with air initially forces the clean filtered sample back through the filter, then such pressurized fluid medium itself is forced back through the filter for a brief time, after which the flow of such fluid medium is stopped, allowing normal liquid filter flow to resume.

United States Patent 1 Barnhardt et al.

[11] 3,733,906 [451 May 22, 1973 [54] METHOD AND APPARATUS FOR THECONTINUOUS WITHDRAWAL OF SAMPLES FROM INDUSTRIAL PROCESS BATHS OR THELIKE FOR ANALYSIS v [75] Inventors: Robert W. Barnhardt, Concord;

William J. Grnbbs, Charlotte, both of NC.

[73] Assignee: Zellweger AG, Uster, Switzerland [22] Filed: Nov. 23,1970 [21] App]. No.: 91,983

[52] U.S. Cl. ..73/42l B [51] Int. Cl. ..'..G0lll 1/14 [58] Field ofSearch ..73/42l B, 421.5 A,

[56] References Cited UNITED STATES PATENTS 1,809,325 6/1931 Austin..73/42l.5 A

3,046,791 7/1962 Dintern ..73/422 3,437,452 4/1969 Bell et al. ..73/42lB 3,457,787 7/1969 Maatsch et al. ..73/42l.5 A

Primary Examiner-S. Clement Swisher Attorney--Werner W. Kleeman [57]ABSTRACT A method and apparatus is disclosed for drawing a filteredsample from a solution or bath, especially an industrial process bath,for continuous or continual analysis. This invention involvesperiodically blowing a suitable pressurized fluid medium compatible withthe bath, that is one which does not affect the sampling process,typically air, although other media can be employed, into the samplingbath on the downstream side of a filter. Backwash of the filter with airinitially forces the clean filtered sample back through the filter, thensuch pressurized fluid medium itself is forced back through the filterfor a brief time, after which the flow of such fluid medium is stopped,allowing normal liquid filter flow to resume.

8 Claims, 3 Drawing Figures JEB QQ-E PATENTED MAYZ 2 I975 METHOD ANDAPPARATUS FOR THE CONTINUOUS WITHDRAWAL OF SAMPLES FROM INDUSTRIALPROCESS BATHS OR THE LIKE FOR ANALYSIS BACKGROUND OF THE INVENTION Thepresent inventionrelates to a new and improved method of, and apparatusfor, the continuous withdrawal of samples from solutions or baths,especially industrial process baths for analysis of the withdrawnsample, making use of filter means for segregating the suspendedparticles or the like contained in the bath from the sample to beanalyzed.

The proper functioning of automatic analysis equipment widely dependsupon maintaining the sample to be analyzed free from suspended particlesor the like. When it is considered that existing automatic analysisequipment work with, for instance, suitable sampling or dosing pumps,the valve elements or the sampling channels of which can be readilyclogged by these suspended particles or other foreign materialscontained in the bath solution, the importance of removing suchparticles becomes apparent. Moreover, the indication techniques utilizedin conjunction with the analysis procedure for arriving at the analysiscan similarly be adversely affected by the suspended particles,particularly then, if, for instance, the suspended particles containedin the sample tend to deposit uponmeasuring electrodes used in theanalysis process, or in the case of photometric measurements causedisturbing lightscattering in the'measuring cell or vessel.

With the recognition of these existing problemsthose concerned with thisparticular art have attempted to resort to certain measures to alleviateor avoid these drawbacks, relying particularly upon filtering of thesample to be analyzed. Hence, constructions of automatic analysisequipment-have become known to the art which make use of filter elementsat the infeed side of the sample at a branch stream, which filterelements are formed of a fine-pored material, for instance fritted glassor foamed materials composed or organic highpolymers. These type filtersenable the sample to be processed in such a manner that an almostcompletely clear solution appears at the filter downstream side. Yet,sample filtering to that degree brings with it the drawback that thepores of the filter material quickly become clogged. Hence, even after arelatively short operating time, the throughflow resistance of thefilter for the sample markedly increases to such an extent that finallythe filter is no longer capable of passing any additional sample; Inthose situations, it is then almost indispensible to resort totechniques which monitor the effectiveness of the filter, for instanceby measuring the pressure gradient or drop across the filter. When thefilter element becomes clogged, it must be replaced, in turn, increasingmaintenance operations of the analysis equipment, and, therefore, thesefactors must be generally construed as a drawback of such type systems.

A still further disadvantage of the state-of-the-art filter systems canbe found in the increased downtime or so called dead period of theautomatic analysis equipment-which automatically is present because ofits original or specific volume. Under the expression dead period" ordowntime," as used in the context of this application, there is to beunderstood that-time interval which passes until, witha-sudden changein'the concentration of the solution which is to be monitored,

the automatic analysis equipment responds. Longerdead periods areespecially then critical if following the automatic analysis equipmentthere is coupled a controller which, in the event of deviation of theconcentration of the solution from a reference value, performs anautomatic correction of the concentration. During these experimentationsit was recognized, especially in the case of non-optical measuringtechniques, that it was wholly unnecessary to filter the sample untilobtaining a completely clear solution. Quite to the contrary, it wasfound that removal of only such suspended particles was really necessarywhich might lead to disturbances or malfunction of the particular pieceof analysis equipment then being employed.

SUMMARY OF THE-INVENTION Accordingly, there is a real need in the artfor an improved method of, and apparatus for, drawing filtered samplesfrom an industrial process bath or the like for continuous or continualanalysis, which is not associated with the aforementioned drawbacks ofthe prior art techniques and systems. Hence, a primary objective of thepresent invention is to provide just such a method and apparatus for theperformance thereof which capably and reliably fulfills the existingneed and is not associated with the aforementioned drawbacks of theprior art enumerated above.

Another and more specific object of the present invention relates to animproved method of preventing filter elements used in automatic analysisequipment from becoming clogged to thereby enable continuous orcontinual analysis, which method specifically contemplates periodicallyblowing a suitable fluid medium, typically air, although other fluidmediums can be used, into the sampling system on the downstream side ofthe filter, to thereby prevent particle build-up on such filter.

Still a further significant object of the present invention relates toan improved method of, and apparatus for, the continuous drawing of asample from industrial process baths forcontinuous analysis, theinventive aspects contemplating increasing the useful life of the filterelement or elements filtering the sample by backwashing the filter with'a suitable fluid medium which prevents particles from building-up onthe filter, the fluid medium itself being selected so as to avoidinterfering with the analysis operation and adversely affectanalyzed.According to important method aspects of I this invention, periodicsurges of a pressurized medium are applied to the downstream side of thefilter at which the sample is removed, the pressurized fluid mediumflowing through the filter contra the direction in which the sample isnormally removed, therebydetaching or loosening suspended particleswhich may have deposited upon the filter at the side of the bath.

trolling the control valve, preferably by a timer, in such a manner thatit opens for a short period, for instance 0.5 seconds, followed by arelatively long valve closing time, for instance about 100 seconds, andthese valveopeningandclosing operations cyclically follow one another insequence. The flow time of the pressurized fluid medium, which can beconveniently referred to as the pressure-on period, is maintainedrelatively short to allow for uninterrupted sample flow, and equally thetime-interval where no pressurized medium flows, similarly convenientlyreferred to as the pressure-off period, is likewise maintainedrelatively short to avoid any excessive particulate build-up at thefilter between the cyclic cleaning operations. This on-off cyclecontinues until the entire process is shut down.

BRIEF DESCRIPTION OF THE DRAWING The invention will be better understoodand objects other than those set forth above, will become apparent whenconsideration is given to the following detailed description thereof.Such description makes reference to the annexed drawing wherein:

FIG. 1 schematically illustrates a filter system or installationequipped with a pressurized fluid medium apparatus and suitable forcarrying-out continuous or continual analysis operations;

FIG. 2 is an enlarged plan view of a preferred form of filter elementsuitable for use in practicing the method aspects of the invention andemployed in the filter installation of the arrangement of FIG. 1; and

FIG. 3 is a cross-sectional view of the filter element depicted in FIG.2, showing specific constructional details thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Describing now thedrawing, in FIG. 1 there is schematically illustrated a filterinstallation constituted by a liquid container 1 housing the liquid,namely the bath 2, which is to be analyzed. The analysis apparatus hasgenerally been indicated by-reference character 3, and theconstructional details thereof are unimportant to the understanding ofthe basic concepts of the present invention. In fact, it should beexpressly understood that the exact nature of the construction of theanalysis apparatus 3 is wholly unimportant as far as the teachings ofthe invention are concerned, it being remarked that any suitableanalysis equipment can be conveniently employed. A sampling or suctionline 4 is operatively connected at one end in flow communication withthe analysis apparatus 3, the opposite end of this suction or samplingline communicating with a filter compartment, generally referred to byreference numeral 5. The exact details of the filter compartment 5 willbe considered more fully hereinafter in conjunction with the descriptionof FIGS. 2 and 3.

Continuing, it will be seen that a pressure line or conduit 6 leads inflow communication to the'filter compartment 5, pressure line 6 beingoperably connected at its opposite end with a suitable control valve 7.The function of the control valve 7 is to periodically admit a supply ofpressurized fluid medium through the line 6 to the filter compartment 5.With that function in mind, it will be apparent that many differenttypes of control valves suitable for this purpose are known to the artand can be effectively utilized in the practice of the invention. Theactual supply of pressurized fluid medium is delivered by a suitablesource 8. This supply source 8 communicates via a conduit 9 with apressure reducer and regulator 10 and then finally with theaforementioned control valve 7. Control valve 7 can be, for instance,actuated by an electromagnet 11 which, in turn, is switched-in andswitched-out by the action of appropriate control pulses delivered forthis purpose by a conventional timer 12.

The timing cycle of the timer 12 can be, for instance, selected suchthat the electromagnet 11 is switched-out for a period of, for instanceseconds, and switchedin for a period of, for instance, 0.5 seconds.Obviously, then, the control valve 7, in turn, will be correspondinglyopen for 0.5 seconds, during which time the pressurized fluid mediumwill flow from the source 8 through the line 9, then through thepressure regulator 10 to the control valve 7, and finally via theconduit 6 into the filter compartment 5. Since the compressed orpressurized fluid medium cannot flow-off via the suction or samplingline 4 (this suction line 4 in most cases being coupled to a flow pumpof the analysis apparatus 3) such pressurized fluid medium is firstforced to expel the liquid in the filter compartment 5 through thefilter element and into the bath, and thereafter such pressurized fluidmedium itself escapes through the filter element into the confines ofthe bath. By virtue of this backwashing of the filter element with thepressurized fluid medium, all, or at least the majority of the suspendedparticles, which have deposited upon the filter surface duringsucking-up of the sample, and which may have possibly penetrated intothe filter pores, are washed back into the bath 2. The pressurized fluidmedium which has penetrated through the filter element ascends orbubbles-up through the bath 2, escaping into the atmosphere, or, ifdesired, doing so through the intermediary of a suitable venting orsuction device 13.

Having now had the benefit of the description of the filter installationof FIG. 1 and its general manner of operation, attention is now directedto FIGS. 2 and 3 showing in plan view and in cross-sectional view,respectively, details of the filter compartment or means 5. Such will beseen to comprise a filter housing 51 and a filter disc or element 53seated at the housing 51 through the action of a threaded flange orfilter holder 52. While the use of a threaded filter holder 52constitutes one convenient manner of attaching the filter element 53with the filter housing 51, obviously it would be easily possible toresort to other attachment techniques. Further, the filter housing 51 isequipped with a throughpassing bore 54, open at both ends as clearlyshown in FIG. 3, one end communicating with an inlet nipple orconnection 55, the other end with an outlet nipple or connection 56.Furthermore, a transversely extending bore 57 coupled in flowrelationship the bore 54 with a filter chamber or space 58 at the filterdownstream side.

Now, as long as the control valve 7 is closed, then, the sample removedfrom the bath 2 by the suction line 4 is continuously withdrawn throughthe filter element 53. When the control valve 7 is open, thenpressurized fluid medium flows from the line or conduit 6 through thebore 54 and the transverse bore 57 into the filter chamber or space 58,then through the filter element 53 itself, into the bath 2. As explainedabove, the surface of the filter element is thereby cleaned. Filterelement 53 is preferably a thin filter element, a so-called surfacefilter as opposed to a depth filter, so that the frequent backwashinghas a more intensive cleaning action; in some instances, in fact,allowing the filter element to be used without having to be replaced ormanually cleaned.

Due to the intermittent cleaning of the filter surface, continuous orcontinual operation of the analysis apparatus 3 is possible, since theperiodic blow of the pressurized fluid medium back through the filterelement 53 does not disadvantageously affect the analysis apparatus 3.Moreover, the sample which is initially forced back through the filterduring backwashing, immediately thereafter again flows back through thefilter element or disc 53, again filling the filter chamber 58. Asalready mentioned heretofore, the short flow-time for the pressurizedfluid medium through the filter element I allows for uninterruptedsample flow, especially when the analysis equipment is provided with ade-bubbler which avoids upsetting of the analyzer and the controller,whereas the similarly relatively short-time intervals during which nopressurized fluid medium flows through the filter successfully preventsexcessive particle build-up between the cleaning operations.

Furthermore, the inventive method and the exemplary embodiment of theapparatus for practicing same, not only affords the heretofore explainedadvantages, but additionally, it may be stated that a further advantageis realized inasmuch as no change in the make-up of the bath 2 occursdue to the penetration of the pressurized gaseous medium through thefilter and the bath and its rising or bubbling-up through the bath toits surface. On the other hand, the prior art techniques resorting tocleaning of a filter element by using a liquid flushing agent bringabout a change in the make-up or composition of the bath.

In practicing the invention, it is possible, in most cases, to utilize,as the pressurized fluid medium, air, it then being a relatively simplematter to provide as the source therefor a suitable supply of compressedair. However, in the event the chemical composition of the bath 2 issuch that air, as the pressurized fluid medium, cannot be feasiblypermitted to flow through the bath, particularly if the oxygen containedtherein or any other constituents thereof might adversely affect thefiltered sample, then the described method can be carried out with, andthe described apparatus can utilize, as the pressurized medium achemically inert gas, while importantly, the entire mode of operationdescribed above remains unaltered.

While there is shown and described present preferred embodiments of theinvention, it is to be distinctly understood that the invention is notlimited thereto, but

- may be otherwise variously embodied and practiced INGLY,

What is claimed is 1. In a method for the continuous withdrawal ofsamples from industrial process baths for analysis, the steps of:

a. arranging a filter in the bath through which flows a sample of thebath from the filter infeed to the filter outfeed side;

b. periodically applying surges of a pressurized fluid medium to theoutfeed side of the filter;

c. causing the thus applied surges of pressurized fluid medium tobackflow through the filter in a direction opposite to the direction offlow of the sample through the filter;

d. by means of the backflow of such pressurized fluid medium through thefilter removing suspended bath particles which have deposited upon thesurface of the filter at the sample infeed side thereof; and

e. removing by suction from the bath the pressurized fluid medium whichhas penetrated into the bath.

2. The method as defined in claim 1, wherein the applied surges ofpressurized fluid medium which backflows through the filter initiallybackwashes the liquid sample entrapped in the filter into the bath, andthereafter excess pressurized medium flows through the filter into thebath. 3. The method as defined in claim 1, including the step ofutilizing a timer controlling a valve for regulating the periodicdelivery of the pressurized fluid medium to the outfeed side of thefilter independent of the clogging of the filter.

4. The method as defined in claim 3, including the step of controllingthe periodic delivery of the surges of the pressurized fluid medium suchthat the time during which flow of the pressurized fluid medium totheoutfeed side of the filter is cut-off and the time during which suchflow is cut-on is in the ratio of at least 100:1.

5. The method as defined in claim 1, including the step of utilizingcompressed air as the pressurized fluid medium.

6. In an apparatus for the continuous withdrawal of samples fromindustrial process baths and the like, comprising filter means providedwith at least one filter element for filtering-out suspended particlesfrom the bath, a source of pressurized fluid medium, conduit means forcoupling in flow relationship said source of pressurized fluid mediumwith said filter means, control valve means for controlling the deliveryof pressurized fluid medium from said source to said filter means, timermeans operating said control valve means for selectively periodicallyopening and closing said control valve means, and suction means forremoving at leas a portion of the pressurized fluid medium bubbling up Ithrough the bath to its surface. I

7. The apparatus as defined in claim 6, wherein said source ofpressurized fluid medium delivers compressed air.

8. The apparatus as defined in claim 6, further including pressureregulator means for said pressurized fluid medium interposed betweensaid source of pressurized fluid medium and said control valve means.

l i III 1

1. In a method for the continuous withdrawal of samples from industrialprocess baths for analysis, the steps of: a. arranging a filter in thebath through which flows a sample of the bath from the filter infeed tothe filter outfeed side; b. periodically applying surges of apressurized fluid medium to the outfeed side of the filter; c. causingthe thus applied surges of pressurized fluid medium to backflow throughthe filter in a direction opposite to the direction of flow of thesample through the filter; d. by means of the backflow of suchpressurized fluid medium through the filter removing suspended bathparticles which have deposited upon the surface of the filter at thesample infeed side thereof; and e. removing by suction from the bath thepressurized fluid medium which has penetrated into the bath.
 2. Themethod as defined in claim 1, wherein the applied surges of pressurizedfluid medium which backflows through the filter initially backwashes theliquid sample entrapped in the filter into the bath, and thereafterexcess pressurized medium flows through the filter into the bath.
 3. Themethod as defined in claim 1, including the step of utilizing a timercontrolling a valve for regulating the periodic delivery of thepressurized fluid medium to the outfeed side of the filter independentof the clogging of the filter.
 4. The method as defined in claim 3,including the step of controlling the periodic delivery of the surges ofthe pressurized fluid medium such that the time during which flow of thepressurized fluid medium to the outfeed side of the filter is cut-offand the time during which such flow is cut-on is in the ratio of atleast 100:1.
 5. The method as defined in claim 1, including the step ofutilizing compressed air as the pressurized fluid medium.
 6. In anapparatus for the continuous withdrawal of samples from industrialprocess baths and the like, comprising filter means provided with atleast one filter element for filtering-out suspended particles from thebath, a source of pressurized fluid medium, conduit means for couplingin flow relationship said source of pressurized fluid medium with saidfilter means, control valve means for controlling the delivery ofpressurized fluid medium from said source to said filter means, timermeans operating said control valve means for selectively periodicallyopening and closing said control valve means, and suction means forremoving at leas a portion of the pressurized fluid medium bubbling upthrough the bath to its surface.
 7. The apparatus as defined in claim 6,wherein said source of pressurized fluid medium delivers compressed air.8. The apparatus as defined in claim 6, further including pressureregulator means for said pressurized fluid medium interposed betweensaid source of pressurized fluid medium and said control valve means.